The human body may be adversely affected depending on the strengths of radio waves (the strengths may also be referred to hereinafter as “transmit power of radio waves” or “radio-wave output”) output by wireless communication apparatuses, such as mobile phones, tablet terminals, and notebook personal computers (PCs). Accordingly, with respect to the transmit power of radio waves of wireless communication apparatuses, permissible ranges are specified in individual countries, for example, based on a specific absorption rate (SAR). The SAR refers to the amount of energy absorbed by tissue per unit mass in a unit time and represents how much energy the human body receives in a certain time from equipment that emits a radio wave.
As a method that complies with the SAR specification, there is a method for performing wireless communication at a radio-wave output level within the permissible range of the SAR by reducing the transmit power of a radio wave of a wireless communication apparatus in advance. There is also a method for reducing the transmit power of a radio wave of a wireless communication apparatus when a communication antenna of the wireless communication apparatus approaches near the human body.
With the former method, that is, the method for performing communication while reducing the transmit power of the radio wave of the wireless communication apparatus in advance, it is possible to comply with the SAR standard, but there are cases in which the output level of the radio wave which is requested by mobile phone companies in each country is not satisfied. In the case of a wireless wide-area network (WWAN), when the transmit power of the radio wave is reduced on a regular basis, the communication arrival distance is reduced. In order to overcome the problem, the latter communication method, that is, the method for reducing the transmit power of the radio wave of the wireless communication apparatus when the communication antenna of the wireless communication apparatus approaches near the human body, is employed.
In order to determine the state of the wireless communication apparatus, for example, whether or not the human body approaches near the wireless communication apparatus, a sensor may be used. This technology is disclosed in, for example, Japanese Laid-open Patent Publication No. 2012-235184. For example, when a proximity sensor is provided in the wireless communication apparatus, whether or not an object has approached near the communication antenna of the wireless communication apparatus can be determined based on a detection value of the proximity sensor.
In particular, with respect to sensing using a proximity sensor, for example, electronic communication specifications managed by the Federal Communications Commission (FCC) in the United States define a method for sensing whether or not a wireless communication apparatus has approached near the human body. The method for sensing whether or not a wireless communication apparatus has approached near the human body, the method being defined by the electronic communication specifications, involves using a proximity sensor and ensuring that the human body is not affected when the proximity sensor is broken.